Cryogenic liquid composite sampling systems and methods

ABSTRACT

A cryogenic liquid sampling system including a chamber having affixed therein a sample pump to proportionally pull a cryogenic liquid sample from an external source to a constant pressure piston accumulator and an enclosure. The enclosure includes a supply port to receive an input stream of a gas, an input port connected to the chamber via a vacuum line, a sample pump port connected to the chamber via a pump line and configured to feed therethrough gas received at the supply port to the sample pump, a vacuum device connected to the input port and configured to generate a vacuum within the chamber by pulling air from the vacuum line, and processing circuitry to control the vacuum device and the sample pump to perform transfer of a cryogenic liquid sample from the external source to an external device.

FIELD OF THE INVENTION

This invention relates generally to sampling take-off and analysis ofcryogenic liquid samples, such as cryogenic ethane, butane or propane,or some combination thereof. More particularly, the invention relates toa system, device and method for sampling a cryogenic liquid from apipeline and storing the sample in its liquid state in a constantpressure container. The stored liquid can then be analyzed to determineits constituent components.

BACKGROUND OF THE INVENTION

A 2017 U.S. Department of Energy study on annual energy consumption inthe United States demonstrates the growing use of natural gas year overyear to supply energy. Since 1981, the amount of natural gas used tosupply energy in the U.S. has increased year over year. On a worldwidescale, the U.S. Energy Information Administration notes that consumptionof natural gas is predicted to increase from 120 trillion cubic feet in2012 to 203 trillion cubic feet in 2040. Thus, by energy source, naturalgas accounts for the largest increase in world primary energyconsumption. It remains the key fuel in the electric power andindustrial sector.

Natural gas can be moved in its normal gaseous state via geographicallyspread pipelines or in a cryogenic liquified state (after having gonethrough a liquefaction process) by specialized carriers such as ships ortrucks. Over the last 15 years, liquid natural gas (LNG) trade volumeshave grown at double the rate of pipeline volumes and it is expectedthat the share of LNG will continue to grow in the coming years. Onereason for this is that liquefaction of natural gas reduces the gasvolume by a factor of 600 thereby making it possible to transport verylarge energy content over short and long distances in specially-designedtankers and trucks.

Additionally, other liquids in addition to LNG, such as natural gasliquids (NGLs) or liquified petroleum gas (LPGs), used as fuel inheating appliances, cooking equipment and vehicles and increasingly usedas an aerosol propellent and a refrigerant have found increasedimportance over the years. These fuels are also transported in acryogenic liquid state over short and long distances for custodytransfer.

When preparing for the transportation, the cryogenic liquids must gothrough a custody transfer such as for example from pipeline or a tankto a tanker/truck or vice versa. As part of this process, it isimportant to determine the energy value of the cryogenic liquid beingtransferred. To determine the energy value of the cryogenic liquid beingtransferred, one or more samples of the cryogenic liquid beingtransferred must be obtained and analyzed.

One option for sampling LNG is to use a sample conditioner which canconvert the LNG into a gaseous form, or vapor sample, which can then beanalyzed by a gas chromatograph. One exemplary system for LNG samplingis the Mustang® Intelligent Vaporizer Sampling System available fromMustang Sampling, LLC of Ravenswood, W. Va. and disclosed and describedat least in U.S. Pat. Nos. 7,484,404 and 7,882,729, the entirety of eachwhich is herein incorporated by reference. An exemplary system for NGLsampling is the Mustang® NGL Sample Conditioning System available fromMustang Sampling, LLC and disclosed and described at least in U.S. Pat.Nos. 9,285,299 and 10,281,368, the entirety of each which is hereinincorporated by reference. Alternatively, in certain circumstances, itmay be desirable to extract and store the sample directly as a liquidfor later analysis by specific analyzing equipment. In such acircumstance, however, the liquid must be sampled so as to maintain anappropriate pressure thereby avoiding any phase change and keeping thesample in a liquid state. Additionally, for some applications, analysisof liquids off-site such as in a lab setting may be preferable.Accordingly, it is necessary to sample and store liquids for transportall while maintaining the sample in its liquid state. One option forstoring a sample for later lab analysis while maintaining appropriatepressure is to proportionally sample and store the sample in a constantpressure container.

Accordingly, there exists a need for a cryogenic liquid sampling system,device and method for effectively extracting, sampling and storingliquid samples for analysis to accurately determine energy values forcustody transfer while also determining the constituent makeup of thecryogenic liquid being transferred.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel cryogenicliquid sampling system, device and method that provide for efficienttakeoff and storage of a sample in its liquid state. The liquid can thenbe analyzed to determine its constituent makeup for various purposes,such as, for example, custody transfer.

It is further an object of the present invention to provide for thetakeoff and maintenance of a liquid sample while preventing any phasechange of the sample.

It is yet another object of the present invention to provide for theeffective capture, storage and portability of the retrieved liquidsample.

It is a further object of the present invention to provide for thecapture of samples over a period of time and/or from different sourcesto provide an proportionally accumulated composite in one or moreconstant pressure containers.

In the following description, reference is made to the accompanyingdrawing, and which is shown by way of illustration to the specificembodiments in which the invention may be practiced. The followingillustrated embodiments are described in sufficient detail to enablethose skilled in the art to practice the invention. It is to beunderstood that other embodiments may be utilized and that structuralchanges based on presently known structural and/or functionalequivalents may be made without departing from the scope of theinvention.

Illustrative, non-limiting embodiments of the present invention mayovercome the aforementioned and other disadvantages associated withrelated art liquid vaporization and measurement systems. Also, thepresent invention is not necessarily required to overcome thedisadvantages described above and an illustrative non-limitingembodiment of the present invention may not overcome any of the problemsdescribed above.

To achieve the above and other objects an embodiment in accordance withthe invention includes a cryogenic liquid sampling system comprising achamber having affixed therein a sample pump configured to pull acryogenic liquid sample from an external source, an enclosure having asupply port configured to receive an input stream of a gas, an inputport connected to the chamber via a vacuum line, a sample pump portconnected to the chamber via a pump line and configured to feedtherethrough gas received at the supply port to the sample pump, and avacuum device connected to the input port and configured to generate avacuum within the chamber by pulling air from the vacuum line, a pistonaccumulator for receiving cryogenic liquid from the sample pump, meansfor maintaining constant pressure in the piston accumulator andprocessing circuitry configured to control the vacuum device and thesample pump to perform proportional transfer of a cryogenic liquidsample from the external source through the piston accumulator to atleast one sample cylinder.

In accordance with another embodiment, the invention includes acryogenic liquid sampling device including a chamber having affixedtherein a sample pump configured to pull a cryogenic liquid sample froman external source; a piston accumulator for receiving cryogenic liquidfrom the sample pump; means for maintaining constant pressure in thepiston accumulator: and an enclosure having a supply port configured toreceive an input stream of a gas, an input port, a sample pump portconfigured to feed gas received at the supply port to the sample pump,an input/output port configured to feed gas received at the supply portto an external device, a vacuum device connected to the input port andconfigured to generate a vacuum within the chamber, and processingcircuitry configured to control the vacuum device and the sample pump toperform transfer of a cryogenic liquid sample from the external sourceto an external device.

In accordance with another embodiment, described herein is a method forsampling a cryogenic liquid including steps of maintaining constantpressure in a piston accumulator for receiving cryogenic liquid from asample pump by applying gas to the piston accumulator to create apredetermined backpressure within the piston accumulator; creating, viaa vacuum device, a vacuum within a chamber by pulling air from thechamber via a vacuum line; extracting, via the sample pump containedwithin the chamber, a cryogenic liquid sample from an external sourceand feeding the extracted cryogenic liquid sample through a speed loop;purging a sample line connecting the chamber and the constant pressurecontainer; and directing at least a portion of the cryogenic liquidsample extracted by the pump to the piston accumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the present invention will become more readily apparentby describing in detail illustrative, non-limiting embodiments thereofwith reference to the accompanying drawings, in which:

FIG. 1 is a schematic of a liquid sample system according to a firstembodiment of the invention which uses a vacuum chamber and vacuumdevice.

FIG. 2 is a schematic of a second embodiment of the invention.

DETAILED DESCRIPTION

Exemplary, non-limiting, embodiments of the present invention arediscussed in detail below. While specific configurations and dimensionsare discussed to provide a clear understanding, it should be understoodthat the disclosed dimensions and configurations are provided forillustration purposes only. A person skilled in the relevant art willrecognize that, unless otherwise specified, other dimensions andconfigurations may be used without departing from the spirit and scopeof the invention.

As used herein “substantially”, “relatively”, “generally”, “about”, and“approximately” are relative modifiers intended to indicate permissiblevariation from the characteristic so modified. They are not intended tobe limited to the absolute value or characteristic which it modifies butrather approaching or approximating such a physical or functionalcharacteristic.

In the detailed description, references to “one embodiment”, “anembodiment”, or “in embodiments” mean that the feature being referred tois included in at least one embodiment of the invention. Moreover,separate references to “one embodiment”, “an embodiment”, or “inembodiments” do not necessarily refer to the same embodiment; however,neither are such embodiments mutually exclusive, unless so stated, andexcept as will be readily apparent to those skilled in the art. Thus,the invention can include any variety of combinations and/orintegrations of the embodiments described herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms, “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the root terms “include”and/or “have”, when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of at least oneother feature, integer, step, operation, element, component, and/orgroups thereof.

It will be appreciated that as used herein, the terms “comprises,”“comprising,” “includes,” “including,” “has,” “having” or any othervariation thereof, are intended to cover a non-exclusive inclusion. Forexample, a process, method, article, or apparatus that comprises a listof features is not necessarily limited only to those features but mayinclude other features not expressly listed or inherent to such process,method, article, or apparatus.

It will also be appreciated that as used herein, any reference to arange of values is intended to encompass every value within that range,including the endpoints of said ranges, unless expressly stated to thecontrary.

As used herein “connected” includes physical, whether direct orindirect, permanently affixed or adjustably mounted. Thus, unlessspecified, “connected” is intended to embrace any operationallyfunctional connection.

As used herein, “liquid” can include liquid ethane, liquid ethylene,liquid propane, liquid butane, liquid iso-butane, NGL, liquid methane,wet natural gas and LPGs. As used herein, a “cryogenic liquid” includesliquids sufficiently cooled to be in a cryogenic state, such as LNG.

In the following description, reference is made to the accompanyingdrawings which are provided for illustration purposes as representativeof specific exemplary embodiments in which the invention may bepracticed. The following illustrated embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. It is to be understood that other embodiments may be utilizedand that structural changes based on presently known structural and/orfunctional equivalents may be made without departing from the scope ofthe invention.

Given the following detailed description, it should become apparent tothe person having ordinary skill in the art that the invention hereinprovides a novel cryogenic liquid composite sampling system and methodthereof for providing augmented efficiencies while mitigating problemsof the prior art.

FIG. 1 illustrates a cryogenic liquid sampling system 100 according toan embodiment of the invention. System 100 includes a constant pressurecontainer 106, a cryogenic liquid sampling device comprised of a sealedchamber 110 and enclosure 160, and the corresponding connectionstherebetween. As an overview of the invention, cryogenic liquid samplesare pulled from an external source, such as a pipeline 102, by a pump112 contained within the chamber 110 and transferred to the constantpressure container 106. As these samples warm throughout the processesdescribed herein, they will lose their cryogenic status but will remainas liquids within the constant pressure container 106. In one example,the pump 112 can be a PGI-Z500 pump manufactured by PGI InternationalLtd. or a V Dual Seal Plunger available from Williams Milton Roy ofIvyland, Pa. The cycle timing of pump 112 extraction and a size of thesample extracted by pump 112 are controlled by processing circuitry suchas a programmable logic controller (PLC) 162 contained within theenclosure 160. As further described herein, the PLC 162 controls theenvironment of the chamber 110 and pressure within the constant pressurecontainer 106 to ensure that any cryogenic liquid samples extracted fromthe pipeline 102 remain in their liquid state from extraction, totransfer and subsequently within the constant pressure container 106.

The chamber 110, which can have an optionally removable lid 116,encloses the pump 112 therein and is positioned approximate a cryogenicliquid source such as pipeline or storage container 102. The chamber 110includes a sample input port 118 for receiving cryogenic liquid samplespulled from the pipeline 102. Liquid take-off from the pipeline 102 viathe sample input port 118 can be achieved for example using a MustangCertiprobe® Sample Extractor 104 available from Mustang Sampling, LLC ofRavenswood, W. Va. A valve 105 which can be manual or automaticallycontrolled by PLC 162 can be included at the extraction point to allowor prevent extraction by the extractor 104. Thus, when the valve 105 isopen, the pump operates to pull cryogenic liquid samples from thepipeline 102 via the extractor 104 at a predetermined sample size andtiming controlled by the PLC 162. To control the stroke timing of thepump 112 and size of the sample extraction, the PLC 162 controls theflow of gas, such as nitrogen, from the enclosure 160 to the chamber 110via a pump line 142 connected to pump input port 120. The nitrogen ispassed from the pump input port 120 to the pump 112 via a stroke line111 contained within the chamber 110.

Once a cryogenic liquid sample is pulled from the pipeline 102, thecryogenic liquid can be transferred through a pump manifold 115 to aspeed loop port 122 and back to the pipeline 102 via a speed loop line144 and/or to a sample output port 124 which leads to the constantpressure container 106 via a sample line 146. In one example, thedirection of flow of extracted cryogenic liquid samples can becontrolled by optional valves 145 and 147. The speed loop can be firstused at the start of an extraction by closing valve 147 and openingvalve 145. This initial run of cryogenic liquid through the speed loopline 144 helps to stabilize the temperature and flow of cryogenicliquids prior to sampling. Once the temperature and flow of cryogenicliquid from the pipeline 102 is stabilized (i.e. ice has started to formon speed loop line 144), the valve 145 can be closed either manually orautomatically by PLC 162. As for the sample line 146, the valve 147directs whether the sample is purged and returned to the pipeline 102via a purge line 148 or passed to the constant pressure container 106.To facilitate a purge, the pump 112 includes a pump purge valve 114which when operated causes the pump 112 to purge the sample line 146 bypushing any excess cryogenic liquid contained within the sample line 146out of the system via the purge line 148. The purge valve 114 canpositioned proximate to the pump 112 but on an exterior of the chamber110 for manual operation. In another example, the valve 114 may beintegrated within the pump 112 itself and digitally controlled via thePLC 162.

The chamber 110 further includes a pressure gauge 117 for visuallymonitoring the pressure within the vacuum chamber 110 thereby allowingfor the detection of leaks and a pressure relief valve 119 to provide asafety mechanism in the event of over-pressurization of the chamber 110.Additionally, the chamber 110 further includes an optional vacuum port126 to evacuate air from the chamber 110 via vacuum line 143 to create avacuum within the chamber 110. A vacuum generated within the chamber 110provides thermal isolation of the chamber 110 from external ambienttemperatures thereby helping to maintain the liquid sample in its liquidform. Accordingly, the vacuum also thermally isolates the pump 112 whichis further cooled directly by thermal contact with the cryogenic liquidfrom the pipeline 102 thereby preventing warming of the pump 112 whichcould adversely affect the temperature of the liquid sample.

Turning to the enclosure 160, the enclosure can be a cabinet enclosing aplurality of components of the system 100 and preferably conforming instandards to Zone 1, Class 1, Division 1 Group B, C, D, t6 (<85° C.)requirements. The enclosure 160 includes the electrical programmablelogic controller (PLC) 162 which receives power and communications datavia an electrical conduit 164 and communications conduit 165 fromelectrical input 166, such as 120 VAC, and communications input 167,respectively. The PLC 162 is connected to a pressure transducer (PTD)170 via electrical/comm conduit 168 and a plurality of valves (172, 178,179) via electrical/comm conduit 169 to control overall functionality ofthe system 100. In one exemplary implementation, the valves (172, 178,179) may be two and/or three-way solenoid valves.

Valve 172 is connected to a sample pump port 174 which connects theenclosure 160 to pump input port 120 of the chamber 110 via the pumpline 142. The valve 172 receives a supply of gas, such as nitrogen, froma supply port 181 via interconnected feed lines which is then fed to thepump 112 through stroke line 111 to control the stroke timing of thepump 112. The supply of the gas is controlled by the PLC 162 via valve172 to determine timing and an amount of gas which passes to sample pumpport 174 as opposed to atmosphere venting port 176. In one example, thepump 112 can be spring-actuated such that the supply of gas via strokeline 111 causes an internal piston to move in a downward direction whichcauses the pump to take a predetermined sample size from the extractionprobe 104. Then, the PLC 162 stops the flow of gas to the pump 112 viavalve 172 such that the lack of pressure on the internal spring of thepump 112 causes the piston to move back to a starting position. The PLC162 can be programmed via communications input 167 based on thespecifications of the user as to the timing of the pump 112 and samplesize extraction parameters thereby allowing the system 100 to providesample extraction for a variety of user applications at differentintervals and for varying constant pressure container sizes.

Valve 178 can be a two-way solenoid valve which controls the passage ofgas, such as nitrogen, from supply port 181 to feed a vacuum device 180.The vacuum device 180 can be an ejector which receives the nitrogen andcreates a vacuum via the venturi effect. Thus, the nitrogen received bythe vacuum device 180 flows from the input port 182 of the ejector to aninterior venturi nozzle (not shown) which increases the flow velocity ofthe nitrogen therein and in the process creates a vacuum in between theventuri and ejector receiver nozzles which causes air to be drawn infrom the vacuum device port 184. As the vacuum device port 184 isconnected to the vacuum port 126 via vacuum line 143 and an input port186, the ejector pulls the air from the chamber 110 thereby creating avacuum therein. The nitrogen input into the ejector as well as airpulled from the chamber 110 exit the ejector and enclosure 160 via avent 187 to muffler 188. An example of an ejector that could be used isthe model 120L manufactured by Vac-Cubes. Further, to ensure that thepressure of gas input into the vacuum device 180 does not exceed productspecifications, the pressure of gas received from supply port 181 can beregulated by a pressure reducing regulator 177, such as a GO Regulatormanufactured by Circor International, Inc.

To ensure that that vacuum created within the chamber 110 by vacuumdevice 180 is effectively maintained, the valve 179 is positionedupstream of the input port 186 to prevent the feed of additional airinto the vacuum device 180 based on measurements by a pressuretransducer (PTD) 170. The pressure transducer 170 is positionedapproximate vacuum port 184 and connected to electrical/comm conduit 168thereby allowing for the transmission of measured pressure signals tothe PCL 162. Based on these measurements by the PTD 170, the PLC 162 cancontrol one or more of valves (178, 179) to ensure a proper vacuumwithin chamber 110. Thus, in one example, when a vacuum is createdwithin the chamber 110 by operation of the vacuum device 180, the PTD170 will detect a predetermined amount of pressure coming from thevacuum line 173 which, if between predetermined upper and lower bounds,or equal to a predetermined setting, will cause the PLC 162 to closevalves 178 and 179. If at some point there is a leak in chamber 110 orother event which causes the vacuum in the chamber 110 to be lost, thePTD 170 will detect this change in pressure and will transmit thisinformation to the PLC 162 which will cause the valves 178 and 179 toopen thereby allowing the vacuum device 180 to create a vacuum withinthe chamber 110 as described previously herein.

In addition to supplying gas to the vacuum device 180 and pump 112, thesupply port 181 provides gas, such as nitrogen, to the constant pressurecontainer 106 via interconnected internal feedlines connected to aninput/output port 190 and container line 149. As described furtherbelow, gas is initially supplied to the constant pressure container 106prior to sample extraction in order to properly backpressure theconstant pressure container 106 which will keep any samples addedtherein in a liquid state at ambient temperature. Further, during theprocess of filling the constant pressure container 106 with liquidsamples, if the pressure within the constant pressure container 106becomes greater than a pressure setting of a pressure relief valve 192,the gas will be bleed off through the container line 149 back to theenclosure 160 via input/output port 190. The excess gas is then pushedfrom the enclosure 160 via vent port 194 and correspondinginterconnected feed lines. To ensure that this excess gas is not pushedback toward supply port 181, the enclosure 160 includes a check valve175 positioned on the supply line to the constant pressure container 106upstream of the supply port 181. Further, an optional isolation valve173 may be positioned downstream of input/output port 190 to keep theline closed until the user is ready to pre-charge the constant pressurecontainer 106 as described further herein.

Although various methods exist for operating the system 100 to extractcryogenic liquid from an external source to a constant pressurecontainer 106 while maintaining the sample in its liquid state, anexemplary method will now be described to illustrate operation of thesystem 100. As illustrated in FIG. 1, the chamber 110 can be installedat or proximate a pipeline 102 to extract cryogenic liquid therefrom viaextractor 104. Optional speed loop line 144 can then be connected toform a speed loop and optional vacuum line 143 can be connected if thechamber 110 needs to be further insulated for extraction. Sample line146 can then be connected between valve 147 and chamber 110 and pumpline 142 can be connected between the enclosure 160 and chamber 110.Further, the constant pressure container 106 can be connected to valve147 and container line 149 to connect the constant pressure container106 to both the enclosure 160 and chamber 110. It should be noted thatthese steps can be completed in any order and that in one example thevalve 147 is optional such that the constant pressure container 106could be connected directly to sample line 146.

Once the system 100 connections are made between the enclosure 160, thechamber 110 and the constant pressure container 106, the connectedconstant pressure container 106 is back-pressured to a predeterminedpressure (i.e. 250 psi) by a supply of gas, such as nitrogen, fromsupply port 181 via interconnected feedlines and container line 149.Initial back-pressuring of the constant pressure 106 container ensuresthat any sample pulled from the external source 102 will remain in itsliquid state at ambient temperature. Next, a pressure regulation levelfor the vacuum device 180 (i.e. ejector) is set to a predeterminedpressure level (i.e. 90 psi) via pressure regulator 177 to induce thecreation of a vacuum in the chamber 110 via vacuum line 143. Once thisis completed, the valve 105 is opened to allow a sample to be pulledfrom the external source 102 via the extractor 104. Once the valve 105is opened, the valve 145 on the speed loop line 144 is opened andadjusted to a predetermined setting which allows for adequate speed loopflow. To ensure the sample line 146 is empty, the valve 147 can then beadjusted so that any flow of cryogenic liquid from sample line 146proceeds to purge line 148 and back to the external source 102. Oncevalve 147 is set in this manner, the pump purge valve 114 is opened fora period of time that will allow the sample line 146 to be adequatelypurged and the incoming sample stream through the speed loop 144 to bein a liquid state. In some examples, this is determined by an amount ofice formation on the speed loop line 144 and at the speed loop port 122.Once an adequate liquid sample is detected, the pump purge valve 114 isclosed and valve 147 is adjusted so that flow through the sample line146 will proceed to the constant pressure container 106. At this point,the PLC 162 is activated to operate the pump 112 as described previouslyherein to control the extracting of cryogenic liquid from the externalsource 102. Extraction is then performed for a predetermined samplingperiod (see Tables 1 and 2 below) at which point the system 100operation can be manually or automatically terminated. The constantpressure container 106 can then be collected and transported for lateranalysis while maintaining the sample therein in liquid form. In oneexample, the sample contained in the composite sampler container 106 canbe partitioned to separate smaller constant pressure containers fortesting and/or storage in accordance with standard custody agreements.

Timing, extraction size and other parameters can be programmed into thePLC 162 for a variety of applications. Exemplary parameters for twodifferent constant pressure containers 106 (i.e. Table 1 for Container 1and Table 2 for Container 2) can be as follows:

TABLE 1 Time Start 9:30 am Time Stop 9:50 am Cylinder Size  500 cc PumpBite Size  1.8 cc Pump Stroke Time   4 seconds % Fill 80%

TABLE 2 Time Start 10:30 am Time Stop 11:40 PM Cylinder Size  1000 cc(Raymond to confirm) Pump Bite Size  0.8 cc Pump Stroke Time    4seconds % Fill 80%

As indicated above in regard to the communication input for the PLC 162,the system may include either or both local flow or time proportionalsampling. FIG. 2, depicts a flow proportional, multiple piston cylinder,composite sampling embodiment. The system 200 features a constantpressure piston accumulator 204 connected to pair of composite sampletake-off piston cylinders 202 includes a flow measurement detectorpreferably positioned proximate the sample take-off (not illustrated)such as a conventional ultrasonic flow meter that captures fixed volumecryogenic liquid increments based on the detected flow volume from thecryogenic liquid source, e.g., pipeline, tank, vessel, etc. In thatcase, a signal from the flow rate sensor/detector is communicated to thePLC to trigger sample take-off upon measurement corresponded to theselected flow volume.

Alternatively, time proportional sampling based on a conventional timermay be relied on when the cryogenic liquid flow rate in source isgenerally consistent. Time proportional sample collection is triggeredby a pre-established clock signal representative of a pre-defined timeinterval is communicated to the PLC to trigger the sample takeoff. Whiletime proportional excludes the requirement for a flow sensor, its usemay be contraindicated where the source is subject to intermittent flowvariations. The required variables for calculating time proportionalsystem sample timing must be provided remotely by some method such asserial communications, analog signal, or be accessible for the PLC torequest through serial communications.

The piston accumulator 204 in FIG. 2 is an enlarged (3 gallon/11.4liter) reinforce tank for collecting a large volume of proportionallycollected sample that feeds the sample takeoff piston cylinders 202 toinsure substantial homogeneity of the cryogenic liquid sample during theentire sample take-off process which is fed from the accumulator 204.The system of FIG. 2 also incorporates a sub-system for back pressuringthe constant pressure piston accumulator 204. The sub-system employs aclosed system design where the piston accumulator 204 maintains constantpressure on the cryogenic liquid sample within the accumulator 204 usingan inert gas, e.g., Helium. The inert gas is maintained at a selectpressure from its source, typically a cylinder/tank contained withincabinet 206, and is connected to the accumulator 204 by open line 205.In such an arrangement, the volume of the collected cryogenic liquidsample within the accumulator 204 determines the location of the pistonwithin the accumulator. Because the pressure is constant, thereciprocation of the piston causes the inert gas to freely travel backand forth between the accumulator 204 and cylinder/tank. By maintaininga constant high pressure within the accumulator, vaporization of thecryogenic liquid is prevented. This use of a closed-loop system of thistype, also minimizes the need for electro-mechanical componentsproviding a low maintenance, essentially inexhaustible pressure source.

A system according to the invention, depends on the temperature of theliquid and surrounding pipeline to be maintained at a temperature lowenough to sustain the liquid phase along the flow path to and inside thepump. The liquid in the pipeline and the pipeline itself act as acold-sink for the entire system, thus keeping it cold. Therefore, it ispreferred that the thermal conductivity between the pump and the probeis sufficient to cool the system inside the vacuum chamber.

It should be understood for a person having ordinary skill in the artthat a device or method incorporating any of the additional oralternative details mentioned above would fall within the scope of thepresent invention as determined based upon the claims below and anyequivalents thereof. Other aspects, objects and advantages of thepresent invention should be apparent to a person having ordinary skillin the art given the drawings and the disclosure.

What is claimed is:
 1. A cryogenic liquid sampling system comprising: achamber having affixed therein a sample pump configured to pull acryogenic liquid sample from an external source; an enclosure having asupply port configured to receive an input stream of a cryogenic liquid,an input port connected to the chamber via a vacuum line, a sample pumpport connected to the chamber via a pump line and configured to feedtherethrough cryogenic liquid received at the supply port to the samplepump, a vacuum device connected to the input port and configured togenerate a vacuum within the chamber by pulling air from the vacuumline, a piston accumulator for receiving cryogenic liquid from thesample pump; means for maintaining constant pressure in the pistonaccumulator and processing circuitry configured to control the vacuumdevice and the sample pump to perform proportional transfer of acryogenic liquid sample from the external source through the pistonaccumulator to at least one sample cylinder.
 2. The cryogenic liquidsampling system of claim 1, wherein the means for maintaining constantpressure is a closed loop system.
 3. The cryogenic liquid samplingsystem of claim 1, wherein the proportional transfer is based on flowrate of the cryogenic liquid in the external source.
 4. The cryogenicliquid sampling system of claim 1, wherein the at least one samplecylinder includes a means to maintain constant pressure to preventvaporization of the sampled cryogenic liquid.
 5. The cryogenic liquidsampling system of claim 1, wherein the external source is a pipeline.6. The cryogenic liquid sampling system of claim 1, wherein theenclosure further includes an input/output port connected to theexternal device via a container line, the input/output port beingconfigured to feed gas received at the supply port to the externaldevice to pre-charge the external device, and receive and vent gas fromthe external device purged by an incoming cryogenic liquid sample pulledby the sample pump.
 7. The cryogenic liquid sampling system of claim 1,wherein the chamber includes a sample output port connected to theexternal device via a sample line to transfer the cryogenic liquidsample.
 8. The cryogenic liquid sampling system of claim 1, wherein thevacuum device receives the gas from the supply port to generate thevacuum within the chamber via the vacuum line.
 9. The cryogenic liquidsampling system of claim 1, wherein the chamber includes a speed loopport connected to a speed loop configured to direct a portion of thecryogenic liquid sample back to the external source.
 10. A cryogenicliquid sampling device comprising: a chamber having affixed therein asample pump configured to pull a cryogenic liquid sample from anexternal source; a piston accumulator for receiving cryogenic liquidfrom the sample pump; means for maintaining constant pressure in thepiston accumulator: and an enclosure having a supply port configured toreceive an input stream of a gas, an input port, a sample pump portconfigured to feed gas received at the supply port to the sample pump,an input/output port configured to feed gas received at the supply portto an external device, a vacuum device connected to the input port andconfigured to generate a vacuum within the chamber, and processingcircuitry configured to control the vacuum device and the sample pump toperform transfer of a cryogenic liquid sample from the external sourceto an external device.
 11. The cryogenic liquid sampling device of claim10, wherein the gas is nitrogen.
 12. The cryogenic liquid samplingdevice of claim 10, wherein the vacuum device is an ejector.
 13. Thecryogenic liquid sampling device of claim 10, wherein the externalsource is a pipeline.
 14. The cryogenic liquid sampling device of claim10, wherein the chamber includes a sample output port configured toconnect to the external device via a sample line to transfer thecryogenic liquid sample.
 15. The cryogenic liquid sampling device ofclaim 10, wherein the vacuum device is configured to receive the gasfrom the supply port to generate a vacuum within the chamber.
 16. Thecryogenic liquid sampling device of claim 10, wherein the chamberincludes a speed loop port configured to connect to a speed loop todirect a portion of the cryogenic liquid sample back to the externalsource.
 17. The cryogenic liquid sampling device of claim 10, whereinmeans for maintaining constant pressure in the piston accumulatorincludes a source of pressurized Helium gas.
 18. The cryogenic liquidsampling device of claim 17, wherein the sample pump includes a purgevalve configured to purge the sample line.
 19. A method for sampling acryogenic liquid comprising: maintaining constant pressure in a pistonaccumulator for receiving cryogenic liquid from a sample pump byapplying gas to the piston accumulator to create a predeterminedbackpressure within the piston accumulator; creating, via a vacuumdevice, a vacuum within a chamber by pulling air from the chamber via avacuum line; extracting, via the sample pump contained within thechamber, a cryogenic liquid sample from an external source and feedingthe extracted cryogenic liquid sample through a speed loop; purging asample line connecting the chamber and the constant pressure container;and directing at least a portion of the cryogenic liquid sampleextracted by the pump to the piston accumulator.